The Autonomic Nervous System (ANS) is the major part of the nervous system that regulates and manages processes of the internal organs, including the blood vessels, stomach, intestine, liver, kidneys, bladder, genitals, lungs, pupils, and heart, and sweat, salivary, and digestive glands. Autonomic testing is an umbrella term that covers testing of the two main divisions of the nervous system, which are the Parasympathetic and Sympathetic (P&S) nervous systems. The P&S nervous systems regulate physiologic processes, such as blood pressure, heart rate, body temperature, digestion, metabolism, fluid and electrolyte balance, sweating, urination, defecation, sexual response, and other processes. This regulation occurs without conscious control, and it extends to every organ system in the body. In fact, many organ-specific tests are tests of autonomic function.